Steering column for motor vehicle

ABSTRACT

A motor vehicle steering column having thereon an electric power assist apparatus including a tubular mast jacket, a structural housing, a socket in an end wall of the housing consisting of an annular seat and a cylindrical guide wall, and an annular plate attached to the mast jacket. The plate plugs into the socket and bears flush against the seat with the edge of the plate fitted in the cylindrical guide wall of the socket so that the centerlines of the mast jacket and the housing are precisely aligned. A C-shaped retainer in an annular groove in the cylindrical guide wall overlaps the plate to prevent dislodgment of the mast jacket from the housing. The retainer has a beveled shoulder which bears on an edge of the groove and converts circumferential expansion of the retainer into longitudinal thrust on the plate to eliminate lash between the plate and the housing.

TECHNICAL BACKGROUND

This invention relates to a motor vehicle steering column having thereonan electric power assist apparatus.

BACKGROUND OF THE INVENTION

A typical motor vehicle steering column includes a tubular mast jacketsupported on a body of the motor vehicle, a steering shaft supported onthe mast jacket for rotation about a longitudinal centerline of the mastjacket, and a steering handwheel attached to the top of the steeringshaft. Manual effort applied at the steering handwheel is transferred bythe steering shaft to a steering gear of the motor vehicle connected tothe bottom of the steering shaft. A “column mounted” electric powerassist apparatus for supplementing the manual effort applied at thesteering handwheel includes a housing rigidly attached to the bottom ofthe mast jacket, an electric motor supported on the housing, reductiongears in the housing for transferring the output torque of the electricmotor to the steering shaft, a transducer in the housing for determiningthe magnitude and direction of the applied manual effort, and anelectronic control for turning the electric motor on and off. Formaximum structural integrity and functional reliability, it isimperative that the longitudinal centerline of the steering column beprecisely aligned with a longitudinal centerline of the housing of theassist apparatus. To that end, it is known to weld an end plate to thebottom of the mast jacket, to guide the end plate to a seated positionon the housing with guide pins on the housing and guide holes in the endplate, and to bolt the end to the housing. Manufacturers, however,continue to seek improved steering columns in which precise alignment ofthe housing of the electric power assist apparatus relative to the mastjacket is achieved reliably and at less manufacturing cost.

SUMMARY OF THE INVENTION

This invention is a new and improved motor vehicle steering columnhaving thereon a column mounted electric power assist apparatusincluding a tubular mast jacket, a structural housing of the assistapparatus, a socket in an end wall of the housing consisting of anannular seat in a plane perpendicular to a longitudinal centerline ofthe housing and a cylindrical guide wall around the annular seatmachined concentric with the longitudinal centerline of the housing, andan annular end plate rigidly attached to the bottom of the mast jacketin a plane perpendicular to a longitudinal centerline thereof having acircular edge machine concentric with the longitudinal centerline of themast jacket after the end plate is attached. The end plate plugs intothe socket and bears flush against the seat with the circular edge ofthe end plate fitted closely in the cylindrical guide wall of the socketso that the longitudinal centerlines of the mast jacket and the housingare precisely aligned. A C-shaped retained in an annular groove in thecylindrical guide wall overlaps the end plate to prevent dislodgement ofthe mast jacket from the housing, the retained has a beveled shoulderwhich bears on and edge of the groove and converts resilientcircumferential expansion of the retainer into longitudinal thrust onthe end plate against the seat of the socket thereby to eliminate lashbetween the end plate and the housing in the direction of thelongitudinal centerlines.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary exploded perspective of a motor vehicle steeringcolumn according to this invention;

FIG. 2 is a broken-away view of a structural housing of an electricpower assist apparatus of the motor vehicle steering column according tothis invention; and

FIG. 3 is an enlarged view of the portion of FIG. 2 identified by thereference circle 3 in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, a motor vehicle steering column 10 according tothis invention includes a column mounted electric power assist apparatus12, a mast jacket 14, and a steering shaft 16 supported on the mastjacket for rotation about a longitudinal centerline 8 of the mastjacket. The mast jacket includes a tubular lower portion 20 and atubular upper portion 22 supported on the lower portion for lineartranslation in the direction of the centerline 18. A steering handwheel,not shown, is rigidly attached to an upper end 24 of the steering shaft.

The column mounted electric power assist apparatus 12 includes astructural housing 26 and an electric motor 28 rigidly attached to thehousing at a mounting flange 30, FIG. 2. The housing 26 includes a pairof integral external tubular mounting lugs 32A,32B and an internalchamber 34 open through an end wall 36 of the housing in a planeperpendicular to a longitudinal centerline 38 of the housing. An annularseat 40 in a plane perpendicular to the centerline 38 of the housing anda cylindrical guide wall 42 machined to precise concentricity relativeto the centerline 38 constitute a socket 44 on the housing in the endwall 36.

An annular end plate 46 is rigidly attached, preferably by fusionbonding, e.g. arc welding or spin welding, to the bottom of the mastjacket 14 at the exposed end of the tubular lower portion 20 of the mastjacket. The end plate includes an annular flat flange portion 48 in aplane perpendicular to the longitudinal centerline 18 of the mast jackethaving an outer circular edge 50. After the end plate 46 is attached tothe tubular lower portion 20 of the mast jacket, the outer circular edge50 of the flange portion is machined to a diameter only slightly smallerthan the diameter of the cylindrical guide wall 42 of the socket 44 andto precise concentricity relative to the longitudinal centerline 18 ofthe mast jacket.

The housing 26 of the assist apparatus 12 is united with the mast jacket14 by plugging the end plate 46 into the socket 44. The cylindricalguide wall 42 closely surrounds the outer edge 50 of the flange portionof the end plate and cooperates therewith in guiding the end plate to aseated position, FIG. 3, in which the flange portion bears flush againstthe annular seat 40 with the longitudinal centerlines 38,18 of thehousing and the mast jacket in precise colinear alignment. At the sametime, the bottom of the steering shaft 16 is connected to a steeringgear, not shown, of the motor vehicle through a support in the internalchamber 34 of the assist apparatus housing so that manual effort appliedat the steering handwheel is transferred to the steering gear.

A transducer, not shown, in the internal chamber 34 monitors thedirection and magnitude of the manual effort applied at the steeringhandwheel and provides a corresponding electronic signal to anelectronic control module which turns the electric motor 28 on and offaccordingly. Reduction gears, not shown, in the internal chamber 34transfer torque from an output shaft of the electric motor to thesteering shaft to supplement the manual effort applied at the steeringhandwheel. Importantly, the precise alignment of the longitudinalcenterlines 18,38 attained simply and automatically when the end plate46 is plugged into the socket 44 to its seated position maximizes thestructural integrity of the steering column and the functionalreliability of the column mounted electric power assist apparatus 12.

The cylindrical guide wall 42 of the socket 44 is interrupted by anannular groove 52 in the housing 26. A first side 54 of the groove 52 isseparated in the direction of the centerline 38 of the housing from theseat 40 by a span which is slightly less than a thickness dimension“T₁”, FIG. 3, of the flange portion 48 of the end plate so that anoutboard side 56 of the flange portion is slightly above the first sideof the groove in the seated position of the end plate. A second side 58of the annular groove 52 is separated from the first side by less than athickness dimension “T₂ ” of a flat C-shaped retainer 60. The retainerincludes a pair of flexible arms 62A, 62B and a beveled shoulder 64along an outer edge of the retainer.

With the end plate 46 in its seated position in the socket 44, the arms62A,62B of the retainer are flexed resiliently toward each other toreduce the diameter of the retainer to less than the diameter of theguide wall 42 so that the retainer fits within the guide wall flushagainst the outboard surface 56 of the flange portion 48 and expandscircumferentially into the annular groove 52 when the arms are released.At the same time, the beveled shoulder 64 bears against and slides alongthe edge of the annular groove where the second side 58 thereofintersects the cylindrical guide wall to convert the expansion of theretainer into thrust on the flange portion toward the seat 40. Theretainer expands until it overlaps the flange portion and the annulargroove 52 with the flange portion thrust firmly and flush against theseat 40. Dislodgment of the end plate 46 from the socket 44 is thusforeclosed and all lash between the assist apparatus housing 26 and themast jacket 14 in the direction of the centerlines 18,38 is eliminatedwith the simple step of releasing the arms 62A,62B of the retainer.Because the assist apparatus housing 26 is secured to the mast jacket 14without threaded fasteners, the steering column 10 according to thisinvention is less susceptible to misalignment between the centerlines18,38 than comparable prior steering columns in which impropertightening of such threaded fasteners is known to contribute to suchmisalignment.

The steering column 10 is supported on a motor vehicle body, not shown,at the tubular bosses 32A,32B on the assist apparatus housing for up anddown pivotal movement about a lateral axis 66 to adjust the verticalposition of the steering handwheel on the steering shaft. A supportbracket 68 surrounds the tubular upper portion 22 of the mast jacket andis attached to the vehicle body above the steering column through a pairof capsules 70A,70B. A clamp between the mast jacket and the supportbracket is actuated by a lever 72 to secure the mast jacket to andrelease the mast jacket from the support bracket. With the mast jacketclamped to the support bracket, an impact on the steering handwheelreacts to the vehicle body through the upper tubular portion 22 of themast jacket and initiates separation of the mounting bracket 68 from thestationary capsules 70A,70B. The tubular upper portion of the mastjacket is thus released for linear translation relative to the tubularlower portion through a collapse stroke against a resistanceattributable to plastic deformation of a pair of flat metal straps74A,74B anchored to the vehicle body whereby a fraction of the kineticenergy of the impact is converted into work.

While only a preferred embodiment of this invention has been describedherein, it will be appreciated that other forms could be readily adaptedby one skilled in the art. Accordingly, the scope of this invention isto be considered limited only by the following claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:
 1. A motor vehicle steering column comprising: a tubular mast jacket, a structural housing for a power assist apparatus including an internal chamber exposed through an end wall of the structural housing in a plane perpendicular to a longitudinal centerline of the structural housing, a socket in the end wall of the structural housing including an annular seat in a plane perpendicular to the longitudinal centerline of the structural housing and a cylindrical guide wall around the annular seat machined concentric with longitudinal centerline of the structural housing, an annular end plate rigidly attached to the bottom of the tubular mast jacket in a plane perpendicular to a longitudinal centerline of the tubular mast jacket having a circular edge of a flange portion of the end plate machined concentric with the longitudinal centerline of the tubular mast jacket after the end plate is attached to the tubular mast jacket, the flange portion of the end plate bearing flush against the seat of the socket in the end wall of the structural housing with the circular edge thereof fitted closely against the cylindrical guide wall of the socket so that the longitudinal centerline of the tubular mast jacket coincides with the longitudinal centerline of the structural housing, and a retainer means operable without screw-threaded fasteners to prevent dislodgment of the end plate from the socket in the structural housing and to concurrently thrust the flange portion of the end plate against the seat of the socket to eliminate lash between the structural housing and the tubular mast jacket in the direction of the longitudinal centerlines of the structural housing and the tubular mast jacket.
 2. The motor vehicle steering column recited in claim 1 wherein the retainer means comprises: an annular groove in the structural housing interrupting the cylindrical guide wall of the socket having a first side in a plane perpendicular to the longitudinal centerline of the structural housing separated from the seat of the socket by a span less than the thickness of the flange portion of the end plate and a second side parallel to the first side, a flat C-shaped retainer circumferentially compressed in the annular groove and overlapping the flange portion of the end plate to prevent dislodgment of the tubular mast jacket from the structural housing, and a beveled shoulder on the retainer bearing against an edge of the second side of the annular groove and cooperating therewith in converting the circumferential expansion of the retainer into thrust on the flange portion of the end plate against the seat of the socket thereby to eliminate lash between the mast jacket and the structural housing in the direction of the longitudinal centerlines of the mast jacket and the structural housing.
 3. A method of making a motor vehicle steering column comprising the steps of: forming a tubular mast jacket, forming a structural housing for a power assist apparatus including an internal chamber exposed through an end wall of the structural housing in a plane perpendicular to a longitudinal centerline of the structural housing, forming a socket in the end wall of the structural housing including an annular seat in a plane perpendicular to the longitudinal centerline of the structural housing and a cylindrical guide wall around the seat machined concentric with longitudinal centerline of the structural housing, forming an annular end plate having a flat annular flange portion therearound, rigidly attaching the annular end plate to the bottom of the tubular mast jacket with the flange portion in a plane perpendicular to a longitudinal centerline of the tubular mast jacket, machining a circular edge of the flange portion concentric with the longitudinal centerline of the tubular mast jacket after the end plate is attached to the tubular mast jacket, plugging the end plate into the socket until the flange portion bears flush against the seat of the socket with the circular edge of the flange portion fitted closely against the cylindrical guide wall of the socket so that the longitudinal centerline of the tubular mast jacket coincides with the longitudinal centerline of the structural housing, and retaining the end plate in the socket with a retainer means operable without screw-threaded fasteners to prevent dislodgment of the end plate from the socket and to concurrently thrust the flange portion of the end plate against the seat of the socket to eliminate lash between the structural housing and the tubular mast jacket in the direction of the longitudinal centerlines of the structural housing and the tubular mast jacket.
 4. The method of making a motor vehicle steering column recited in claim 3 wherein the step of retaining the end plate in the socket with a retainer means comprises the steps of: forming an annular groove in the structural housing in the cylindrical guide wall of the socket having a first side in a plane perpendicular to the longitudinal centerline of the structural housing separated from the seat of the socket by a span less than the thickness of the flange portion of the end plate and a second side parallel to the first side, forming a flat C-shaped retainer with a beveled shoulder, circumferentially compressing the retainer to a diameter less then the diameter of the cylindrical guide wall of the socket and aligning the retainer with the annular groove in the cylindrical guide wall and flush against the flange portion of the end plate, and releasing the retainer for circumferential expansion into the annular groove with the beveled shoulder of the retainer hearing against an edge of the second side of the annular groove so that the retainer overlaps the annular groove and the flange portion of the end plate to prevent dislodgment of the tubular mast jacket from the structural housing and the beveled shoulder cooperates with the edge of the second side of the annular groove in converting the circumferential expansion of the retainer into thrust on the flange portion of the end plate against the seat of the socket thereby to eliminate lash between the mast jacket and the structural housing in the direction of the longitudinal centerlines of the mast jacket and the structural housing.
 5. The method of making a motor vehicle steering column recited in claim 3 wherein the step of rigidly attaching an annular end plate to the bottom of the tubular mast jacket comprises the step of: fusion bonding the annular end plate to the bottom of the tubular mast jacket. fusion bonding the annular end to the bottom of the tubular mast jacket. 